In recent years, Over The Top Video (OTT-V) becomes the main stream of streaming services using the Internet, and, as a moving picture distribution protocol, which is internationally standardized, that can be used therefor, Moving Picture Experts Group-Dynamic Adaptive Streaming over HTTP (MPEG-DASH; hereinafter referred to as DASH) using an HTTP similar to that for reading a web site or the like has been known (for example, see Non-Patent Document 1).
In DASH, an adaptive streaming technology is realized. In other words, the content supply side is configured to prepare a plurality of streams that have a same content and have mutually-different bit rates according to a difference in the image quality, the angle of view, the size, and the like and distribute the streams. On the other hand, the content reception side is configured to select an optimal stream according to the communication environments of the Internet, the decoding capacity thereof, and the like from among the plurality of streams prepared on the supply side and receive and reproduce the selected stream.
In addition, the supply side is configured to supply a metafile called a Media Presentation Description (MPD) to the reception side such that a stream can be adaptively selected, received, and reproduced on the reception side.
In the MPD, the address (url information) of a server (supply source) supplying a stream (media data such as an audio, a video, a subtitle, and the like) of a content formed as a chunk to the reception side is described. The reception side requests a stream by accessing a server that is a supply source of a content based on corresponding url information and receives and reproduces the stream that is distributed from the server in an HTTP unicast manner in response to the request.
FIG. 1 illustrates an example of the configuration of a content supplying system that distributes a content in a steaming manner based on DASH.
This content supplying system 10 is configured by: a plurality of content supplying apparatuses 20 supplying contents; and a plurality of DASH clients 30 receiving and reproducing contents. Each DASH client 30 can be connected to the content supplying apparatuses 20 through a Contents Delivery Network (CDN) 12 using the Internet 11.
The content supplying apparatus 20 distributes a plurality of streams that have a same content and have mutually-different bit rates. Each content supplying apparatus 20 includes: a content management server 21; a DASH segment streamer 22; and a DASH MPD server 23.
The content management server 21 manages source data of a content to be distributed to the DASH client 30, generates a plurality of pieces of streaming data having mutually-different bit rates based on the source data, and outputs the generated streaming data to the DASH segment streamer 22.
The DASH segment streamer 22 generates segment streams, for example, of fragmented MP4 or the like by dividing each unit of streaming data into segments with respect to time and maintaining the generated segment streams as files. In addition, the DASH segment streamer 22 distributes the maintained file of a segment stream in an HTTP unicast manner to a request source in response to a request (HTTP request) from the DASH client 30 as a web server. Furthermore, the DASH segment streamer 22 notifies metadata including an address representing the supply source of the file of the segment stream to the DASH MPD server 23.
The DASH MPD server 23 generates an MPD in which an address representing the supply source (in other words, the DASH segment streamer 22) of the file of a segment stream. In addition, the DASH MPD server 23 distributes the MPD generated in response to a request (HTTP request) from the DASH client 30 as a web server to the request source in an HTTP unicast manner.
The DASH client 30 requests the DASH MPD server 23 for an MPD and receives the MPD that is distributed in the HTTP unicast manner in response thereto. In addition, the DASH client 30 requests the DASH segment streamer 22 for the file of a segment stream based on the received MPD and receives and reproduces the file of the segment stream that is distributed in the HTTP unicast manner in response thereto.
In addition, the CDN 12 includes a cache server (not illustrated in the drawing), and the cache server caches an MPD and the file of a segment stream distributed through the CDN 12 in the HTTP unicast manner. Then, the cache server can distribute the MPD or the segment stream that is cached to a request source in response to a request from the DASH client 30 in the HTTP unicast manner in place of the DASH MPD server 23 or the DASH segment streamer 22 as a web server.